Human granulocytic ehrlichiosis (HGE) and human monocytic ehrlichiosis (HME) are emerging tick-borne disease in the U.S. Annual incidence of both disease is increasing, with more than 600 cases of human ehrlichiosis reported in the last ten years. The purpose of this study is to detect the presence and distribution of the HGE agent and related ehrlichial pathogens in New York State. Specifically, the applicant will evaluate the utility of canine serology to assess risk for HGE in an endemic area, 2) measure canine seroprevalence in areas where few or no cases of HGE are reported, 3) test Ixodes scapularis and Amblyomma americanum for the presence of Ehrlichia species and related pathogens, and 4) establish a canine serum bank and a tick depository for future retrospective studies on emerging tick-borne diseases in the region.